A leaching technique employing a sulfate media has been established as a hydrometallurgical technique for the recovery of copper from copper ores or copper concentrates and the like. Industrial-scale plants using the SX-EW process (combining solvent extraction and electrowinning) are in current commercial use.
The leaching of copper by sulfate media, however, is generally used for ores anchored by oxide ores. This technique is applied to only a part of a sulfide ore because of many problems it has, such as its low-rate reaction of leaching, impossibility of recovering precious metals and the like. Furthermore, in a copper concentrates wherein the grade of copper is improved by mineral processing and the like, the leaching of copper by the sulfate media is not practical, not only because of its low reaction rate but also because of its low leaching rate of copper and the difficulty of recovering precious metals.
Also, the above-described hydrometallurgical process is problematic in that it needs to be conducted at high temperatures and pressures to improve the leaching rate of copper. Therefore, a process of leaching copper from ores of sulfide by chloride media using an aqueous chloride solution has been developed, being a process which does not require high temperatures and pressures (Patent document 1). Patent document 1 discloses the process of electrowinning monovalent copper by leaching copper from the ores of sulfide as Cu+ with a Cl—Br base acidic electrolyte that is produced by electrowinning of copper, has a high oxido-reduction potential, and includes Cu2+. This process, however, involves a haloid (halex, typically BrCl2—) that is difficult to treat in leaching and that is poisonous. Additional problems include an increase in cost for the reason that the copper produced by leaching with the chloride media needs refining because of its low grade and difficulty in control because of the complicated facilities which it necessitates.
To solve these problems, a process was developed which produces high grade copper by processing the copper concentrate and the like with chloride media, extracting copper ions from the chloride media into an organic solvent by solvent extraction, separating an organic phase from an aqueous phase, converting divalent copper extracted by contacting the organic phase with sulfuric acid to copper sulfate, and conducting electrowinning of copper by an existing sulfate media (Patent documents 2, 3). However, the extraction performance of copper is not be very high in this process, and there is no choice but to increase the amount of the solution treated in the process in order to increase the throughput of copper. As a result, the construction cost of a plant for carrying out that process is increased due to the scale of the facilities necessary to leach copper, and the operating cost is increased because the energy necessary to heat the solution is substantial. (Patent documents 2 and 3 were not yet open to the public on the filing date of the present application.    (Patent document 1) Australian Patent No. 669906 (Production of metals from minerals).    (Patent document 2) Japanese Patent Application No. 2008-84597.    (Patent document 3) Japanese Patent Application No. 2008-84934.